Roofing shingles normally include oxidized asphalt which becomes hard and brittle at low temperatures. Even when the product temperature is below 25.degree. C., it becomes difficult to handle; nailing causes hair line cracks around the nail head; and hammer impressions surrounding the nail head develop cracks in coating films that make lines of weakness in the shingle so that they are not able to resist strong wind forces.
This problem is accentuated when the ambient temperature is below 0.degree. C., so much so that at this temperature it is not possible to handle or install roofing shingles as they are far too brittle.
Furthermore, problems are encountered with already installed shingles when exposed to low climatic temperatures as the "self-seal type" adhesives which are often used on shingle remain inactive for a considerably long time especially at temperatures below 35.degree. C. It is conceivable therefore that shingles which are installed at higher temperatures than 25.degree. C. but at temperatures below 35.degree. C. are still "unsealed" when cold conditions are encountered, and a gust of wind can then actually lift the "unsealed tabs" of the shingles and develop serious cracks and holes around the nail or staple head by which the shingle is attached to the roof. If the wind is sufficiently strong, the cold shingle tab will break off, seriously destroying the main function of the shingles which is to protect the roof from leaks.
Problems are also encountered with asphalt roofing shingles wherein the asphalt coating caliper is increased for product performance needs above the customary 0.025 inches to 0.1 inches which is usually above a ratio of coating calibre to cellulosic membrane calibre of 0.75. With this higher ratio of coating caliper to membrane caliper, hair line cracks are relatively easily caused around nail heads, as are cracks in the coating film relatively easily caused by hammer impressions.
The problem is also aggrevated by utilizing a wider than normal width of roofing shingle exposed area or tab size, and although this increases the weight of the tab, there is a larger area for the wind force to act upon and it is therefore easier to bend or snap a larger area or tab under high wind conditions that it is to snap a smaller area or tab especially under cold conditions.
The tops of conventional roof shingle cutouts between tabs are also relatively weak due to their shape.
Problems of cracking and breaking of shingles are also encountered more readily when "unsealed" shingles are used as not only the exposed area or tab of the shingle can lift under high wind conditions but the whole shingle can lift.
The degree of severity of the cracking phenomen is also high especially when glass-mats or polyester fiber mats, which have low basis weight 1 pound per 100 square feet to 3 pounds per 100 square feet and are conventionally very thin and cellulosic "felts" of base weights lower than conventional bone dry 43.7 pounds per 480 square feet are used, as extra amounts of coating asphalts are required to make up for the low membrane weight. Such roofing products make with conventional coating asphalts are exceedingly brittle and unworkable at product temperatures lower than 25.degree. C.
The ability for a roofing shingle to resist damage caused by nailing, stapling, or wind up-lifting, especially at temperatures below 25.degree. C., is dependent upon the quality of the coating asphalt in the key area which is normally damaged.
There is therefore a requirement for a roofing shingle which does not become hard and brittle in key areas in cooler to cold temperatures and is therefore not damaged during installation nor after installation by high winds.